DUP councillor Ruth Patterson has revealed she intends to leave politics after being snubbed by her own party for a key Assembly seat.

The outspoken politician told the Belfast Telegraph she was "frustrated" and "disappointed" that she had not been selected by the party to replace retired MLA Jimmy Spratt.

Mrs Patterson, who has been a member of the DUP for two decades and an elected representative on Belfast City Council for 14 years, also hit out at the party for not telling her personally that she had been overlooked for the post in favour of Emma Pengelly, a former special adviser to First Minister Peter Robinson.

"I have nothing to lose anymore because I have already lost it all. I thought I would climb to the next step on the ladder but it wasn't meant to be. This is not sour grapes by any means. It is just the sheer frustration of all the years of hard work, but for what? You want to achieve something," said Mrs Patterson.

The former deputy lord mayor for Belfast said she was upset that she had not been told by the party that Ms Pengelly had been appointed instead of her.

"A simple phone call to tell me who was to get the job would have made all the difference. It is basic manners, it is being polite and respectful to people. I have asked for a meeting with Peter Robinson to discuss this and am still waiting for a response," said Mrs Patterson.

She added: "I wish Emma well, but for someone who has never had any association with south Belfast, who doesn't live in south Belfast, I have to say, her appointment has come as a bolt out of the blue."

Jimmy Spratt retired last month following a lengthy and very public battle with bowel cancer. The 65-year-old had been a DUP MLA for South Belfast for almost eight years.

Mrs Patterson put herself forward to take over from Mr Spratt following discussions with a party colleague.

"Considering in the last Assembly elections 3,700 people gave me their first preference vote, I think anyone in my place would have been disappointed to be overlooked. I am the highest polling candidate not to be elected. I think that is very significant. Some people sitting up in Stormont didn't receive the votes I had," the 59-year-old said.

"I think for both myself and Christopher (Stalford - DUP Belfast councillor) it would have certainly been the proper protocol. Neither of us saw this coming.

"I think it is getting time for me to get out of politics. I don't think I will be standing again in the next council elections. I would have run again in the Assembly elections had I replaced Jimmy Spratt but it's time for me to get out."

Mrs Patterson revealed it has been a tough few years for her. She said she lost her job with the charity Cancer Focus when she was arrested in 2013 over comments she posted on Facebook about an imagined attack on a republican parade planned for Castlederg that August. She was detained by police for 12 hours in relation to the offence of sending grossly offensive communications.

The charge was later withdrawn after she was given an informed warning.

"I lost my job on the back of it all. I had been in that job nine years and I loved it and the people I worked with. But I had to go when I was arrested. People don't know the harm and damage that was done when I was arrested. I was in custody for 12 hours. They put me in a cell and shut the door, they searched my house, I was finger-printed, photographed and swabbed. I'm still on medication from that time because it was so horrific. I start to get over that and then this," she said.

Mrs Patterson added: "The South Belfast situation wasn't nice. I know politics is a dirty game but I didn't see this coming. People think I am a hard nut to crack, but underneath I'm really a marshmallow. However, I'll just have to get up and dust myself down."